1. Field of the Invention
The present invention relates to digital television signals and, more particularly, to the search and detection of digital HDTV television signals.
2. Description of the Related Art
High Definition television (HDTV) sets and other digital equipment such as set-top boxes must be able to receive digital and analog television signals from various sources. In order to accomplish this, such television receivers and other digital/analog equipment have two or more signal inputs that are adapted to receive various television signal sources. The television allows the user to switch between the various signal inputs in order to view the channels carried by the signal source coupled to the selected signal input.
Digital and analog television signals may be received from sources such as antennas, community cable systems, Direct Broadcast Satellite (DBS) systems, or the like. These various signal sources are coupled to separate signal inputs of the television and/or other digital/analog equipment (hereinafter collectively termed “television”). Each signal source typically carries many television channels. Some of the channels from the various signal sources are the same while some of the channels are different. With regard to both analog and digital off-air television signals from an antenna, if several digital channels are available, the user may be required to manually adjust the antenna in order to receive the best possible reception from all available channels.
With any signal source, the television needs to know what channels are available for each signal source or signal input, in order to skip those channels that do not carry programming when the user is switching between the various channels. Channel autoprogramming algorithms and systems for automatically detecting active channels and indicating the active channels in a channel scanning list are known for analog television receivers.
It is known to provide a channel search routine for analog channels that will obtain a discrete sample or “snapshot” of all the currently available channels on all of the various signal inputs. The channel search routine then stores all of the channels detected from all of the signal inputs during the search in memory (e.g. EEPROM), deleting any channels previously stored that are not now currently available. At power-up of the unit, the channels in EEPROM become the channel list. This may occur when the user makes an adjustment to the antenna, such as moving position or location, or when the DBS or cable system adds and/or deletes channels.
Part of the channel search process is detecting if cable or an air antenna is connected to the signal input. This detection is performed on all signal inputs. Such a search may be an iterative process. The user potentially will need to adjust the antenna and complete a channel search several times before correctly positioning the antenna for superior reception of all channels available. As this is a time consuming process, there is a need for a different type of channel search.
It is thus an object of the present invention to provide a channel search that will shorten the time necessary to complete the channel acquisition process.